Display screen or portion thereof with transitional graphical user interface



FIG. 1 is a front view of a first embodiment of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence, showing our new design;

FIG. 2 is a front view showing a second image thereof;

FIG. 3 is a front view showing a third image thereof;

FIG. 4 is a front view showing a fourth image thereof;

FIG. 5 is a front view of a second embodiment of a display screen or portion thereof with transitional graphical user interface showing a first image in a sequence;

FIG. 6 is a front view showing a second image thereof;

FIG. 7 is a front view showing a third image thereof; and,

FIG. 8 is a front view showing a fourth image thereof.

The outermost short dash-dash broken lines illustrating a display screen or portion thereof form no part of the claimed design. The remainder of the short dash-dash broken lines depict portions of the graphical user interface that form no part of the claimed design.

The dot-dash broken lines in the figures represent the boundary of the claimed design and form no part of the claimed design.

The appearance of the transitional image sequentially transitions between the images shown in FIGS. 1-4 and 5-8. The process or period in which one image transitions to another image forms no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with transitional graphical user interface, as shown and described. 